The objectives of this research proposal are to provide quantitative information on the acute and long-term effects of drugs with emphasis on adverse drug effects. The program utilizes epidemiologic techniques to achieve these goals. Large amounts of carefully collected and verified information on drugs used, together with illnesses which developed subsequently, are available on computer files for over 300,000 people of all ages, and additional data are being collected. The data derive from standardize monitoring of hospitalized medical and surgical patients, and from automated recording of prescriptions and hospital diagnoses in a large health maintenance organization located in Seattle, Washington. These data allow for an efficient evaluation of both acute and long-term drug effects for most marketed drugs, utilizing both case-contron and cohort types of analysis. Valid quantitation and discovery of drug toxicity is necessary for the optimal practice of clinical therapeutics..